1. Field of the Invention
The present invention relates in general to a method for operating a base station in a code division multiple access (CDMA) mobile communication system, and more particularly to a method for operating abase station to solve a call discontinuity, or speech disable state, based on the inter-speech sphere movement of a mobile station in enlarging a speech radius limited in timing in a CDMA mobile communication system.
2. Description of the Prior Art
In a conventional CDMA mobile communication system, all mobile stations and base stations are timed with a reference time of the CDMA system. A mobile station obtains timing information from a message sent from a base station and sets a reference time on the basis of the obtained timing information for synchronization with the base station. At this time, the reference time set by the mobile station is a value delayed from a reference time of the base station due to a propagation delay from the base station to the mobile station and a signal process delay of the mobile station. Further, the mobile station sends a signal synchronously with the set self reference time, and such a reverse link signal is delayed for a propagation delay time and then received by the base station. As a result, the base station sends a forward link signal synchronously with a system reference clock, but receives a reverse link signal with a time delay (referred to hereinafter as xe2x80x9cbidirectional propagation delayxe2x80x9d) from the system reference clock.
In the CDMA system, the maximum allowable value of such a bidirectional propagation delay is limited in a hardware manner by a modem application specific integrated circuit (ASIC) of the base station. The maximum allowable value is about 416 xcexcs, which is about 62 Km (416 xcexclight velocity/2) when it is calculated in terms of cell speech radii in an open area. Consequently, the maximum allowable cell speech radius is limited in timing by the base station modem ASIC.
A method for enlarging the cell speech radius limited in timing by the hardware of the base station modem ASIC as mentioned above is shown in Korean Patent Application No. 98-36239, filed by this applicant.
FIG. 3 shows a service area for speech radius enlargement and call processing. As shown in this drawing, a speech radius, which is wider than that limited in timing by the hardware of the base station modem ASIC in the CDMA mobile communication system, is partitioned by a predetermined unit into first and second speech spheres 110 and 120. The predetermined unit signifies a value below the maximum cell speech radius limited in timing by the hardware of the base station modem ASIC. In this regard, the above speech radius may be partitioned into a different number of speech spheres.
With reference to FIG. 1, there is shown in block form an example of a base station for speech radius enlargement in a CDMA mobile communication system. As shown in this drawing, the base station comprises a clock generator 200, first and second signal processors 300 and 310 and radio frequency (RF) signal processing means 400.
The clock generator 200 receives a 10 MHz signal, time of day (TOD) signal and 1 pulse per second (PPS) signal from a global positioning system (GPS) receiver 100 and generates a first EVEN SECOND clock synchronously with the 1 PPS signal and a second EVEN SECOND clock, which is delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere 110, as shown in FIG. 2.
The first signal processor 300 assigns pilot, synchronization, paging and traffic channels covering both of the first and second speech spheres 110 and 120 synchronously with the first EVEN SECOND clock from the clock generator 200 and outputs the assigned channels to the RF signal processing means 400. The first signal processor 300 further detects and demodulates only access and traffic channels, which are sent from mobile stations located in the first speech sphere 110 to the base station, synchronously with the first EVEN SECOND clock from the clock generator 200.
The second signal processor 310 detects and demodulates only access and traffic channels, which are sent from mobile stations located in the second speech sphere 120 to the base station, synchronously with the second EVEN SECOND clock from the clock generator 200.
Each of the first and second signal processors 300 and 310 includes at least one channel card 303 and an analog modulator/demodulator circuit 315, as shown in FIG. 5. The channel card 303 is composed of at least one channel element 305 containing a set of base station modem ASICs (commercially available from, for example, QUALCOMM company) 306 for modulating and demodulating digital signals, and a channel card processor 304 for controlling the channel element 305. The analog modulator/demodulator circuit 315 includes a digital/analog (D/A) converter 307 for converting a digital signal from the channel card 303 into an analog signal, a quadrature phase shift keying (QPSK) modulator 309 for modulating the analog signal from the D/A converter 307 in a QPSK manner, a QPSK demodulator 313 for demodulating an RF signal in the QPSK manner, and an analog/digital (A/D) converter 308 for converting a QPSK-demodulated signal into a digital signal. The channel card 303 also receives the first or second EVEN SECOND clock from the clock generator 200.
On the other hand, in each of the first and second signal processors 300 and 310, each channel card is provided with a corresponding one of a channel element for the process of a forward channel and a channel element for the process of a reverse channel. Alternatively, each channel card may be provided with both of the channel elements.
The RF signal processing means 400 includes an RF transmitter 410 for receiving forward link channel signals from the first signal processor 300, to be transmitted to mobile stations, modulating the received signals into RF signals and transmitting the modulated RF signals through a transmission antenna 500, and an RF receiver 420 for receiving reverse link channel signals from the mobile stations through reception antennas 510 and 513 of the base station, RF-demodulating the received signals and transferring the resultant signals to the first and second signal processors 300 and 310, respectively.
Now, a description will be given of the cell speech radius enlarging method of the 98-36239 patent application, which is performed by the base station with the above-mentioned construction.
First, the clock generator 200 receives the 10 MHz signal, TOD signal and 1 PPS signal from the GPS receiver 100 and generates the first EVEN SECOND clock synchronously with the 1 PPS signal. The clock generator 200 further generates the second EVEN SECOND clock delayed from the first EVEN SECOND clock for the maximum bidirectional propagation delay time of the first speech sphere 110.
Then, the first and second signal processors 300 and 310 receive the first and second EVEN SECOND clocks from the clock generator 200, respectively. The first signal processor 300 assigns pilot, synchronization and paging channels synchronously with the received first EVEN SECOND clock and transmits them to all speech spheres belonging to the base station through the RF signal processing means 400 and transmission antenna 500.
At this time, if an access channel is sent from a specific mobile station located in the first speech sphere 110, then it is received at the reception antenna 510 and transferred to the first signal processor 300 through the RF signal processing means 400. As a result, the first signal processor 300 detects and demodulates the access channel, which is sent from the specific mobile station in the first speech sphere 110 to the base station, synchronously with the first EVEN SECOND clock.
Subsequently, the first signal processor 300 assigns a traffic channel synchronously with the first EVEN SECOND clock and transmits it through the RF signal processing means 400 and transmission antenna 500.
Upon receiving the traffic channel transmitted through the antenna 500, the specific mobile station in the first speech sphere 110 assigns a desired traffic channel and sends it to the base station.
Then the traffic channel sent from the specific mobile station in the first speech sphere 110 is received at the reception antenna 510 and transferred to the first signal processor 300 through the RF signal processing means 400. The first signal processor 300 detects and demodulates the transferred traffic channel synchronously with the first EVEN SECOND clock. As a result, a speech state is established between the base station and the specific mobile station in the first speech sphere 110.
On the other hand, in the case where an access channel is sent from a specific mobile station located in the second speech sphere 120 after the first signal processor 300 transmits the pilot, synchronization and paging channels to all mobile stations, it is received at the reception antenna 513 and transferred to the second signal processor 310 through the RF signal processing means 400. As a result, the second signal processor 310 detects and demodulates the access channel from the specific mobile station in the second speech sphere 120 synchronously with the second EVEN SECOND clock.
Subsequently, a channel card processor in the first signal processor 300 assigns one channel element in the processor 300 and, further, a traffic channel synchronously with the first EVEN SECOND clock and transmits the assigned traffic channel externally through the RF signal processing means 400 and transmission antenna 500.
Upon receiving the traffic channel transmitted through the antenna 500, the specific mobile station in the second speech sphere 120 assigns a desired traffic channel and sends it to the base station.
Then, the traffic channel sent from the specific mobile station in the second speech sphere 120 is received at the reception antenna 513 and transferred to the second signal processor 310 through the RF signal processing means 400. The second signal processor 310 detects and demodulates the transferred traffic channel synchronously with the second EVEN SECOND clock. As a result, a speech state is established between the base station and the specific mobile station in the second speech sphere 120.
Further disclosed in the above Korean Patent Application No. 98-36239 is another method for enlarging the cell speech radius limited in timing by the hardware of the base station modem ASIC, which will hereinafter be described in detail.
With reference to FIG. 4, there is shown in block form another example of a base station for speech radius enlargement in a CDMA mobile communication system. As shown in this drawing, the base station comprises a clock generator 200, first and second signal processors 320 and 330 and RF signal processing means 400.
The clock generator 200 receives a 10 MHz signal, TOD signal and 1 PPS signal from a GPS receiver 100 and generates a first EVEN SECOND clock synchronously with the 1 PPS signal and a second EVEN SECOND clock, which is delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere 110, as shown in FIG. 2.
The first signal processor 320 assigns and transmits pilot, synchronization and paging channels covering both of the first and second speech spheres 110 and 120 and traffic channels covering the first speech sphere 110 on a forward link from the base station to mobile stations synchronously with the first EVEN SECOND clock from the clock generator 200. The first signal processor 320 further detects and demodulates only access and traffic channels, which are sent; from mobile stations located in the first speech sphere 110 to the base station, on a reverse link from the mobile stations to the base station synchronously with the first EVEN SECOND clock from the clock generator 200 to cover only the first speech sphere 110.
The second signal processor 330 advances the second EVEN SECOND clock from the clock generator 200 by a delay time using a timing compensation register in a modem ASIC and assigns and transmits traffic channels to the second speech sphere 120 on the forward link synchronously with the advanced clock. The second signal processor 330 further detects and demodulates only access and traffic channels from mobile stations located in the second speech sphere 120 on the reverse link synchronously with the second EVEN SECOND clock from the clock generator 200 to cover only the second speech sphere 120.
Each of the first and second signal processors 320 and 330 is the same in construction as each of the first and second signal processors 300 and 310 as shown in FIG. 5, with the exception that a timing compensation register is provided in each base station mode ASIC to transmit a traffic channel to a mobile station ahead by a delay time (time for which the second EVEN SECOND clock is delayed from the first EVEN SECOND clock).
The RF signal processing means 400 is substantially the same in construction as that in FIG. 1 and a detailed description thereof will thus be omitted.
Now, a description will be given of the second cell speech radius enlarging method of the 98-36239 patent application, which is performed by the base station with the above-mentioned construction.
First, the clock generator 200 receives the 10 MHz signal, TOD signal and 1 PPS signal from the GPS receiver 100 and generates the first EVEN SECOND clock synchronously with the 1 PPS signal. The clock generator 200 further generates the second EVEN SECOND clock delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere 110.
Subsequently, the first and second signal processors 320 and 330 receive the first and second EVEN SECOND clocks from the clock generator 200, respectively. The first signal processor 320 assigns pilot, synchronization and paging channels synchronously with the received first EVEN SECOND clock and transmits them to all speech spheres belonging to the base station through the RF signal processing means 400 and transmission antenna 500.
At this time, in the case where an access channel is sent from a specific mobile station located in the first speech sphere 110, it is received at the reception antenna 510 and transferred to the first signal processor 320 through the RF signal processing means 400. Then, the first signal processor 320 detects and demodulates the access channel, which is sent from the specific mobile station in the first speech sphere 110 to the base station, synchronously with the first EVEN SECOND clock.
Then, the first signal processor 320 assigns a traffic channel synchronously with the first EVEN SECOND clock and transmits it through the RF signal processing means 400 and transmission antenna 500.
If the specific mobile station in the first speech sphere 110 receives the traffic channel transmitted through the antenna 500, then it assigns a desired traffic channel and sends it to the base station.
Subsequently, the traffic channel sent from the specific mobile station in the first speech sphere 110 is received at the reception antenna 510 and transferred to the first signal processor 320 through the RF signal processing means 400. The first signal processor 320 detects and demodulates the transferred traffic channel synchronously with the first EVEN SECOND clock. As a result, a speech state is established between the base station and the specific mobile station in the first speech sphere 110.
On the other hand, if an access channel is sent from a specific mobile station located in the second speech sphere 120 after the first signal processor 320 transmits the pilot, synchronization and paging channels to all mobile stations, then it is received at the reception antenna 513 and transferred to the second signal processor 330 through the RF signal processing means 400. As a result, the second signal processor 330 detects and demodulates the access channel from the specific mobile station in the second speech sphere 120 synchronously with the second EVEN SECOND clock.
Subsequently, the second signal processor 330 assigns a traffic channel ahead by a predetermined delay time (time for which the second EVEN SECOND clock is delayed from the first EVEN SECOND clock) and transmits the assigned traffic channel through the RF signal processing means 400 and transmission antenna 500. Upon receiving the traffic channel transmitted through the antenna 500, the specific mobile station in the second speech sphere 120 assigns a desired traffic channel and sends it to the base station.
The traffic channel sent from the specific mobile station in the second speech sphere 120 is received at the reception antenna 513 and transferred to the second signal processor 330 through the RF signal processing means 400. The second signal processor 330 detects and demodulates the transferred traffic channel synchronously with the second EVEN SECOND clock. As a result, a speech state is established between the base station and the specific mobile station in the second speech sphere 120.
However, in the above-mentioned speech radius enlargement methods, when a speech radius wider than a limited speech radius is partitioned into a plurality of speech spheres for the enlargement of the limited speech radius and channel elements are assigned to signal processors for the call processing, a speech disable state, or call discontinuity, may occur as a mobile station moves from one speech sphere to a different speech sphere.
The above-mentioned speech radius enlargement methods have another disadvantage in that a speech disable state may occur when a mobile station is located in a border area between adjacent speech spheres according to the enlargement of a speech radius.
On the other hand, U.S. Pat. No. 5,590,177 shows a technique for preventing an active call from discontinuity when a mobile station suddenly moves from a first speech sphere to a second speech sphere in a radio telephone system.
In the ""177 patent, the call discontinuity is prevented by carrying out the step of, in response to the sudden movement of the mobile station from the first speech sphere to the second speech sphere, determining whether the active call is in danger of discontinuity, the step of, in response to the determination, notifying a first base station that the active call is in danger of discontinuity, the step of, in response to the notification, determining whether the active call is present in the first base station and a call discontinuity processor, and the step of, in response to the call discontinuity processor, establishing the active call with a second base station in the second speech sphere prior to discontinuity of the active call with the first base station.
In other words, in the above ""177 patent, when the mobile station suddenly moves from the first speech sphere to the second speech sphere, the call discontinuity is prevented by calculating the ratio of the total energy received by the mobile station to signal energy, determining on the basis of the calculated ratio whether the active call is in danger of discontinuity and establishing the active call with the second base station in the second speech sphere in accordance with the determined result. However, this is localized to a general handoff within a limited speech radius.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for operating a base station to solve a speech disable state based on the inter-speech sphere movement or border area location of a mobile station in enlarging a speech radius limited in timing by hardware of a base station modem ASIC in a CDMA mobile communication system.
In accordance with one aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station mode m ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobiles stat ions in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the movement of a specific mobile station located in the first speech sphere to the second speech sphere, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of, if an access channel is sent from the specific mobile station located in the first speech sphere, allowing the first signal processor to detect and demodulate the access channel synchronously with the first EVEN SECOND clock; the fourth step of allowing the first signal processor to assign a traffic channel synchronously with the first EVEN SECOND clock and transmit it to the specific mobile station in the first speech sphere; the fifth step of, if a reverse traffic channel is sent from the specific mobile station in the first speech sphere, allowing the first signal processor to detect and demodulate the reverse traffic channel synchronously with the first EVEN SECOND clock; the sixth step of allowing the first signal processor to measure a first bidirectional propagation delay time with the specific mobile station at an interval of predetermined time and compare the measured first bidirectional propagation delay time with a first threshold value; the seventh step of allowing the first signal processor to repeatedly measure the first bidirectional propagation delay time if the first bidirectional propagation delay time is smaller than the first threshold value at the above sixth step and, if the first bidirectional propagation delay time is greater than or equal to the first threshold value at the above sixth step, allowing the first signal processor to subtract the maximum bidirectional propagation delay value of the first speech sphere from the first bidirectional propagation delay time and set the subtracted result as a second bidirectional propagation delay time; the eighth step of allowing the second signal processor to detect and demodulate the reverse traffic channel from the specific mobile station synchronously with the second bidirectional propagation delay time; the ninth step of allowing the first signal processor to compare the first bidirectional propagation delay time with a second threshold value; and the tenth step of selecting and utilizing the reverse traffic channel demodulated by the second signal processor if the first bidirectional propagation delay time is greater than or equal to the second threshold value at the above ninth step.
In accordance with another aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station modem ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobile stations in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the movement of a specific mobile station located in the second speech sphere to the first speech sphere, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of, if an access channel is sent from the specific mobile station located in the second speech sphere, allowing the second signal processor to detect and demodulate the access channel synchronously with the second EVEN SECOND clock; the fourth step of allowing the first signal processor to assign a traffic channel synchronously with the second EVEN SECOND clock and transmit it to the specific mobile station in the second speech sphere; the fifth step of, if a reverse traffic channel is sent from the specific mobile station in the second speech sphere, allowing the second signal processor to detect and demodulate the reverse traffic channel synchronously with the second EVEN SECOND clock; the sixth step of allowing the second signal processor to measure a first bidirectional propagation delay time with the specific mobile station at an interval of predetermined time, add the maximum bidirectional propagation delay value of the first speech sphere to the measured first bidirectional propagation delay time and set the added result as a second bidirectional propagation delay time; the seventh step of allowing the second signal processor to compare the second bidirectional propagation delay time with a first threshold value; the eighth step of returning to the above sixth step if the second bidirectional propagation delay time is greater than the first threshold value at the above seventh step and allowing the first signal processor to detect and demodulate the reverse traffic channel from the specific mobile station synchronously with the second bidirectional propagation delay time if the second bidirectional propagation delay time is smaller than or equal to the first threshold value at the above seventh step; the ninth step of allowing the second signal processor to compare the second bidirectional propagation delay time with a second threshold value; and the tenth step of selecting and utilizing the reverse traffic channel demodulated by the first signal processor if the seconds bidirectional propagation delay time is smaller than or equal to the second threshold value at the above ninth step.
In accordance with a further aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station modem ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobile stations in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the location of a specific mobile station in a border area between the first and second speech spheres, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of allowing the first signal processor to set up the size of an access channel preamble scanning window to be greater than the maximum bidirectional propagation delay value of the first speech sphere; the fourth step of, if an access channel is sent from the specific mobile station in the border area, allowing both of the first and second signal processors to detect and demodulate the access channel synchronously, respectively, with the first and second EVEN SECOND clocks and measure first and second bidirectional propagation delay times with the specific mobile station, respectively; the fifth step of allowing the first signal processor to assign a traffic channel synchronously with the first EVEN SECOND clock and transmit it to the specific mobile station; the sixth step of, if a reverse traffic channel is sent from the specific mobile station, allowing both of the first and second signal processors to detect and demodulate the reverse traffic channel synchronously, respectively, with the first and second EVEN SECOND clocks; the seventh step of comparing the first and second bidirectional propagation delay times measured at the above fourth step with each other to determine which one of the first and second speech spheres is a near-by speech sphere; and the eighth step of selecting and utilizing the reverse traffic channel demodulated by the first signal processor if the first speech sphere is determined to be the near-by speech sphere at the above seventh step and selecting and utilizing the reverse traffic channel demodulated by the second signal processor if the second speech sphere is determined to be the near-by speech sphere at the above seventh step.
In accordance with another aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station modem ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobile stations in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the movement of a specific mobile station located in the first speech sphere to the second speech sphere, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of, if an access channel is sent from the specific mobile station located in the first speech sphere, allowing the first signal processor to detect and demodulate the access channel synchronously with the first EVEN SECOND clock; the fourth step of allowing the first signal processor to assign a forward traffic channel synchronously with the first EVEN SECOND clock and transmit it to the specific mobile station in the first speech sphere; the fifth step of, if a reverse traffic channel is sent from the specific mobile station in the first speech sphere, allowing the first signal processor to detect and demodulate the reverse traffic channel synchronously with the first EVEN SECOND clock; the sixth step of allowing the first signal processor to measure a first bidirectional propagation delay time with the specific mobile station at an interval of predetermined time and compare the measured first bidirectional propagation delay time with a first threshold value; the seventh step of allowing the first signal processor to repeatedly measure the first bidirectional propagation delay time if the first bidirectional propagation delay time is smaller than the first threshold value at the above sixth step and, if the first bidirectional propagation delay time is greater than or equal to the first threshold value at the above sixth step, allowing the first signal processor to subtract the maximum bidirectional propagation delay value of the first speech sphere from the first bidirectional propagation delay time and set the subtracted result as a second bidirectional propagation delay time; the eighth step of allowing the second signal processor to detect and demodulate the reverse traffic channel from the specific mobile station synchronously with the second bidirectional propagation delay time and assign a forward traffic channel ahead; the ninth step of allowing the second signal processor to compare the second bidirectional propagation delay time with a second threshold value; and the tenth step of, if the second bidirectional propagation delay time is greater than or equal to the second threshold value at the above ninth step, selecting and utilizing the reverse traffic channel demodulated by the second signal processor and then transmitting the forward traffic channel assigned by the second signal processor to the specific mobile station.
In accordance with a further aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station modem ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobile stations in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the movement of a specific mobile station located in the second speech sphere to the first speech sphere, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of, if an access channel is sent from the specific mobile station located in the second speech sphere, allowing the second signal processor to detect and demodulate the access channel synchronously with the second EVEN SECOND clock; the fourth step of allowing the second signal processor to assign a forward traffic channel ahead and transmit it to the specific mobile station in the second speech sphere; the fifth step of, if a reverse traffic channel is sent from the specific mobile station in the second speech sphere, allowing the second signal processor to detect and demodulate the reverse traffic channel synchronously with the second EVEN SECOND clock; the sixth step of allowing the second signal processor to measure a first bidirectional propagation delay time with the specific mobile station at an interval of predetermined time, add the maximum bidirectional propagation delay value of the first speech sphere to the measured first bidirectional propagation delay time and set the added result as a second bidirectional propagation delay time; the seventh step of allowing the second signal processor to compare the second bidirectional propagation delay time with a first threshold value; the eighth step of returning to the above sixth step if the second bidirectional propagation delay time is greater than the first threshold value at the above seventh step and, if the second bidirectional propagation delay time is smaller than or equal to the first threshold value at the above seventh step, allowing the first signal processor to detect and demodulate the reverse traffic channel from the specific mobile station synchronously with the second bidirectional propagation delay time and to assign a forward traffic channel; the ninth step of allowing the second signal processor to compare the second bidirectional propagation delay time with a second threshold value; and the tenth step of, if the second bidirectional propagation delay time is smaller than or equal to the second threshold value at the above ninth step, selecting and utilizing the reverse traffic channel demodulated by the first signal processor and transmitting the forward traffic channel assigned by the first signal processor to the specific mobile station.
In accordance with yet another aspect of the present invention, in a method for operating a CDMA base station which partitions a speech radius wider than that limited in timing by a modem ASIC of the base station into first and second speech spheres by a predetermined unit below the maximum speech radius allowed by the base station modem ASIC to enlarge the limited speech radius, the base station having a first signal processor for processing forward link channels from the base station to mobile stations in the first and second speech spheres and reverse link channels from the mobile stations in the first speech sphere to the base station and a second signal processor for processing reverse link channels from the mobile stations in the second speech sphere to the base station, there is provided a method for solving a speech disable state based on the location of a specific mobile station in a border area between the first and second speech spheres, comprising the first step of allowing a clock generator to generate first and second EVEN SECOND clocks, the second EVEN SECOND clock being delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere, and allowing the first and second signal processors to receive the first and second EVEN SECOND clocks from the clock generator, respectively; the second step of allowing the first signal processor to assign pilot, synchronization and paging channels synchronously with the first EVEN SECOND clock and transmit them to all speech spheres covered by the base station; the third step of allowing the first signal processor to set up the size of an access channel preamble scanning window to be greater than the maximum bidirectional propagation delay value of the first speech sphere; the fourth step of, if an access channel is sent from the specific mobile station in the border area, allowing both of the first and second signal processors to detect and demodulate the access channel synchronously, respectively, with the first and second EVEN SECOND clocks and measure first and second bidirectional propagation delay times with the specific mobile station, respectively; the fifth step of allowing both of the first and second signal processors to assign forward traffic channels and transmit them to the specific mobile station; the sixth step of, if a reverse traffic channel is sent from the specific mobile station, allowing both of the first and second signal processors to detect and demodulate the reverse traffic channel synchronously, respectively, with the first and second EVEN SECOND clocks; the seventh step of comparing the first and second bidirectional propagation delay times measured at the above fourth step with each other to determine which one of the first and second speech spheres is a near-by speech sphere; and the eighth step of, if the first speech sphere is determined to be the near-by speech sphere at the above seventh step, selecting and utilizing the reverse traffic channel demodulated by the first signal processor and transmitting the forward traffic channel assigned by the first signal processor to the specific mobile station and, if the second speech sphere is determined to be the near-by speech sphere at the above seventh step, selecting and utilizing the reverse traffic channel demodulated by the second signal processor and transmitting the forward traffic channel assigned by the second signal processor to the specific mobile station.